In many automotive manual transmissions or dual clutch transmissions power is transferred between meshed gears mounted on two parallel rotating shafts. An example of a dual clutch transmission is provided in commonly assigned U.S. Pat. No. 8,342,051. On one or more of the parallel shafts, there are multiple rotatably mounted gears. The gear ratio of the transmission is dependent upon which gears are selectively torsionally connected to the shafts. As is apparent to those familiar with the art, for the gear to be torsionally connected to a shaft, the gear must first have its speed synchronized with the speed of the shaft. Accordingly synchronizers are provided to torsionally connect the gears to their respective shaft.
Referring to FIGS. 1-9, a dual gear synchronizer 10 that works similarly to that shown and explained in Frost, U.S. Pat. No. 5,135,087 (disclosure incorporated by reference herein). Since operation of the dual gear synchronizer is essentially identical for both sides of the synchronizer 10 only one side is explained. The synchronizer 10 has a hub 12. The hub 12 is spline connected to a shaft 17 (shown in FIG. 9) along the hub's inner diameter inner diameter 14 (FIG. 2). The hub 12 along its outer diameter has six circumferential segments 16 with spline teeth 18. Positioned between the segments 16 are three geometrically spaced sleeve detent members 20. The detent members 20 capture a coil spring 19 (FIG. 9) radially outward loaded bearing ball 22. The detent members can also travel axially with respect to the hub 12 between the segments 16.
Surrounding the hub 12 and torsionally connected thereto is a sleeve 24. The sleeve 24 has two axially spaced apart rims 25 projecting radially outward to provide a nest 26 to capture a shift fork 28 (shown partially in phantom in FIG. 9) of the transmission. An inner diameter 27 (FIG. 1) of the sleeve 24 has a series of axial spline teeth 30 allowing the sleeve 26 to be torsionally fixedly connected and axially movable on the spline teeth 18 of the hub. The sleeve detents 20 press balls 22 into depressions 34 (FIG. 1) provided in the inner diameter the sleeve 24.
Lateral of the sleeve 24 is a blocking ring(s) 36. The blocking ring 36 has the geometrically spaced tabs 38 that torsionally connect the blocking ring with the hub 12 in a lost motion manner. Tab 38 is clocked or captured between hub segment surfaces 47 and 49 of the hub. The angular shift (lost motion) between the hub or sleeve 24 when tab 38 surface 41 contacts hub segment surface 47 to where tab surface 43 contacts hub surface 49 is approximately 6 degrees. The blocking ring 36 also has an operatively associated alpha friction surface 40. The blocking ring 36 also has a series of blocking cogs or teeth 42.
Lateral of each blocking ring 36 is an intermediate ring 48. Lateral of the intermediate ring 48 is an inner ring 52. Lateral of the inner ring 52 is an engagement ring 60. The engagement ring 60 is fixedly connected with a gear 61 (shown partially in FIG. 9) to be torsionally connected with the shaft 17. The engagement ring 60 has cogs 63 (shown in greater detail in FIGS. 3-8). Intermediate ring 48 has tabs 62 axially extending toward the engagement ring 60. The tabs 48 extend into radial slots 64 of the engagement ring to torsionally connect intermediate ring 48 with the engagement ring 60. In a similar fashion the inner ring 52 has axially extending tabs 68. The tabs 68 extend into radial slots 78 provided in the blocking ring to torsionally connect inner ring 52 to the blocking ring 36 and to operatively associate inner ring alpha friction surface 51 with the blocking ring 36.
In operation the shift fork 28 (not shown in FIGS. 3-8) moves sleeve 24 leftward from a neutral position shown in FIG. 3 to a pre-synchronization position shown in FIG. 4. The sleeves 24 leftward movement (FIG. 3) also causes the sleeve detents 20 to be moved leftward in relationship to the hub 12 causing detent side surface 71 to push against blocking ring side surface 73 (see additionally FIG. 9). The leftward movement of the blocking ring 36 causes the friction surface 40 of the blocking ring 36 to contact in sliding frictional engagement the outer friction surface 75 of the intermediate ring 48. Since the intermediate ring 48 via the tab 62 is torsionally connected with the engagement ring 60 the friction surface 75 and its operatively associated engagement ring 60 are accelerated. Additionally intermediate ring 48 is frictionally driven by inner ring 52, the inner ring 52 being torsionally connected with the blocking ring 36. Therefore the intermediate ring 36 on its outer 75 and inner 80 surfaces through sliding frictional engagement will be acted upon by blocker ring 36 to accelerate the engagement ring 60. Assuming rotation of the shaft 17 and the yoke in a direction 81 (FIG. 1), intermediate ring tab surface 43 is contacting surface 49 of the hub. With the drag caused by the inertia of the accelerating gear 61/engagement ring 60 on the blocking ring 36, the blocking ring tab surface 43 contacts hub surface 49 with increased force. As shown in FIG. 5 the cogs 42 of the blocking ring are now in a blocking position contacting tips 85 of the spline teeth 30 of the sleeve, preventing further axial movement of the sleeve 24 (FIG. 5). Until the engagement ring 60 and its connected gear 61 are synchronized with the sleeve 24, the cogs 42 of the blocking ring continue to prevent further leftward travel of the sleeve 24. Eventually the engagement ring 60 (and connected gear 61) are brought to a speed that is synchronized with that of the shaft 17 (equal to that of the hub 12). Upon reaching synchronous speed leftward movement of the sleeve 22 (FIG. 6) will now cause the tips 85 of the sleeve teeth to cam the cogs 42 of the blocking ring over to allow continued leftward movement of the sleeve 24 to the point wherein the sleeve spline teeth 30 extend (FIG. 7) to the spacing between the engagement ring cogs 63. Continued movement of the sleeve 24 will lock in the engagement ring 60 and the torsional connection of gear with the shaft is complete (FIG. 8).
It is readily known to those skilled in the art for the last decades there has been a major push to increase the fuel economy of automotive vehicles. Accordingly, it is desirable to reduce the spatial envelope of the power train as much as possible to maximize interior passenger room of the vehicle while minimizing the spatial envelope of the vehicle body to reduce aerodynamic drag thereby increasing fuel efficiency. Therefore, it is desirable to provide a synchronizer in a smaller spatial envelope than those revealed previously. It is also desirable to provide a synchronizer with high synchronization capacity while at the same time minimizing the number of components.